To add onto others, beyond the base popularity of minecraft is modded minecraft which is significantly more adult oriented, adding dozens of layers of complexity to minecraft. Have you ever wanted to learn the basics of nuclear reactor design and nuclear refinement? We have mekanism, nuclearcraft, and many others. Have you ever wanted to program inside of minecraft? Well time to learn Lua and use computercraft.

Etc, modded minecraft expands minecraft to an insane degree. Me and my 50+ yr old father play it.